Gabriele Cosmo
157 lines
6.2 KiB
Plaintext
157 lines
6.2 KiB
Plaintext
-------------------------------------------------------------------
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=========================================================
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Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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=========================================================
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TestEm7
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-------
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How to produce a Bragg curve in a water phantom.
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How to compute the dose in 'test volumes' called tallies.
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How to define a maximum step size.
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1- GEOMETRY DEFINITION
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The geometry consists of a single block of a homogenous material,
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placed in a world.
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Three parameters define the geometry :
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- the material of the box,
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- the thickness of the box (sizeX),
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- the transverse dimension of the box (sizeYZ).
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The default is 20 cm of water.
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In addition a transverse uniform magnetic field can be applied.
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The default geometry is constructed in DetectorConstruction class,
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but all of the above parameters can be changed interactively via
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the commands defined in the DetectorMessenger class.
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The size, matter, positions of several test-volumes (tallies) can be
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defined via UI commands : /testem/det/tally...
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2- PHYSICS LIST
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Physics lists can be local (eg. in this example) or from G4 kernel
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physics_lists subdirectory.
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Local physics lists:
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- "local" standard EM physics with current 'best' options setting.
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these options are explicited in PhysListEmStandard
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- "standardSS" standard EM physics with single Coulomb scattering
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instead of multiple scattering;
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- "standardNR" standard EM physics with single Coulomb scattering
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process G4ScreenedNuclearRecoil instead of the
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multiple scattering for ions with energy less than
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100 MeV/nucleon; the new process was developed
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by M.H. Mendenhall and R.A. Weller from Vanderbuilt
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University and published in NIM B 277 (2005) 420.
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The process is released in this example with its
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mathematical tool c2_functions
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From geant4/source/physics_lists/builders:
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- "emstandard_opt0" recommended standard EM physics for LHC
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- "emstandard_opt1" best CPU performance standard physics for LHC
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- "emstandard_opt2" similar fast simulation
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- "emstandard_opt3" best standard EM options - analog to "local" above
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- "emstandard_opt4" best current advanced EM options standard + lowenergy
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- "emstandardWVI" standard EM physics and WentzelVI multiple scattering
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- "emstandardSS" standard EM physics and single scattering model
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- "emstandardGS" standard EM physics and Goudsmit-Saunderson multiple scatt.
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- "emlivermore" low-energy EM physics using Livermore data
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- "empenelope" low-energy EM physics implementing Penelope models
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- "emlowenergy" low-energy EM physics implementing experimental
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low-energy models
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Decay and StepMax processes are added to each list.
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Optional components can be added:
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- "elastic" elastic scattering of hadrons
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- "HElastic"
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- "QElastic"
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- "binary" QBBC configuration of hadron inelastic models
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- "binary_ion" Binary ion inelastic models
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- "ionIoni" Ion gas models
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Physics lists and options can be (re)set with UI commands
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3- AN EVENT : THE PRIMARY GENERATOR
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The primary kinematic consists of a single particle which hits the
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block perpendicular to the input face. The type of the particle
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and its energy are set in the PrimaryGeneratorAction class, and can
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changed via the G4 build-in commands of G4ParticleGun class (see
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the macros provided with this example).
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The default is a 160 MeV proton.
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In addition one can define randomly the impact point of the incident
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particle. The corresponding interactive command is built in
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PrimaryGeneratorMessenger class.
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A RUN is a set of events.
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4- DOSE IN 'TEST-VOLUMES'
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The energy deposited in the test-volumes (tallies) defined in
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DetectorConstruction are printed at EndOfRun, both in MeV and gray.
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5- VISUALIZATION
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The Visualization Manager is set in the main().
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The initialisation of the drawing is done via the command
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> /control/execute vis.mac
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The detector has a default view which is a longitudinal view of the box.
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The tracks are drawn at the end of event, and erased at the end of run.
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Optionally one can choose to draw all particles, only the charged one,
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or none. This command is defined in EventActionMessenger class.
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6- HOW TO START ?
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- execute Test in 'batch' mode from macro files
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% TestEm7 proton.mac
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- execute Test in 'interactive mode' with visualization
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% TestEm7
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....
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Idle> type your commands
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....
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Idle> exit
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7- HISTOGRAM OF THE BRAGG PEAK
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Testem7 computes the total energy deposited along the trajectory of
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the incident particle : the so-called Bragg peak.
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In order to control the accuracy of the deposition, the user can limit
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the maximum allowed for the step size of charged particles.
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(command /testem/stepMax )
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The result is a 1D histogram, which is the total energy deposited
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along the trajectory of the incident particle.
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The bin size is equal to stepMax. The number of bins is determined by
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the thickness of the absorber (with a minimum of 100 bins).
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The total energy deposited is plotted in MeV/mm per incident particle.
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The next histogram allows to have a zoom around the Bragg peak. Its binning
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should be defined via UI command:
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/analysis/h1/set 2 nbins xmin xmax unit
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The last histogram shows the projectile range. Its bining should be defined
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similary by the UI command:
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/analysis/h1/set 3 nbins xmin xmax unit
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One can control the name of the histograms file with the command:
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/analysis/setFileName name (default testem7)
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It is possible to choose the format of the histogram file : root (default),
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xml, csv, by using namespace in HistoManager.hh
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It is also possible to print selected histograms on an ascii file:
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/analysis/h1/setAscii id
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All selected histos will be written on a file name.ascii (default testem7)
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